A bioinformatics-driven molecular genetics approach will be used to study the role of alternative splicing as a gene regulation mechanism in plant hormone signaling using the model plant Arabidopsis thaliana. High-density oligonucleotide microarrays will be used to examine the effects of exogenous auxin, brassinolide, and gibberellic acid treatments on (i) the expression of Arabidopsis genes that encode putative RNA-binding protein splicing factors; and (2) pre-mRNA splicing. T-DNA mutant insertion lines will be identified for the genes encoding hormone-regulated putative RNA-binding proteins and assayed for hormone associated phenotypic changes. Putative hormone-regulated alternative splice variants detected using the Affymetrix arrays will be further analyzed using RT-PCR, denaturing high performance liquid chromatography (DHPLC) and final confirmation by sequencing. Genes confirmed to exhibit hormone-regulated alternative splicing will be selected for use in developing an alternative splicing reporter gene system that will be tested experimentally in transgenic plants.